Benign cystic mesothelioma of the appendix presenting in a woman: a case report

INTRODUCTION: Benign cystic mesothelioma or peritoneal inclusion cysts are rare benign abdominal tumors usually occurring in females of reproductive age. These cysts present as abdominopelvic pain or masses but are often found on imaging or incidentally at surgery. They are commonly associated with pelvic inflammatory disease, endometriosis, or ovarian cysts. We report what is, to the best of our knowledge, the first case of a benign cystic mesothelioma complicating a presentation of acute appendicitis. CASE PRESENTATION: A 19-year-old Irish Caucasian woman presented with abdominal pain. Imaging suggested appendicitis with abscess formation. She was treated with antibiotics and scheduled for interval appendicectomy. At laparoscopy, an unusual cystic mass was found arising from the appendix. Histology revealed benign cystic mesothelioma. CONCLUSION: We report what is, to the best of our knowledge, the first case of a benign cystic mesothelioma arising from the appendix and complicating a presentation of acute appendicitis. This is a benign pathology, but recurrences are not uncommon. Benign cystic mesothelioma should be included in the differential when investigating pelvic masses or abscesses associated with either appendicitis or pelvic inflammatory disease in women.